The familiar fuse, which is a common household item, was invented in the 19th. century and has been used the home and industry.
The standard fuse as we know it is a single filament device designed to carry a certain current when a certain voltage is applied between its ends.
When the rated current is exceeded by a specified percentage the fusing link opens and therby disconnecting the current flow providing protection to sensitive systems.
I have noticed, however, that the single element fuse does not provide adequate flexibility for equipment which is intended to operate on a dual switchable line voltage such as 115VAC/230VAC. A great many electrical/electronic systems, instrumentation and consumer products are designed with the feature of selecting line voltage by means of a switch so that equipment manufactured in the U.S. can be operated abroad and vice versa.
The fusing aspect, at the present time, is handled by sending special kits, instructions and a warning to make sure to install the proper fuse prior to applying the line voltage. Errors or oversight often leads to costly repairs and delays in equipment usage.
The above has lead me to the idea of the Dual Link AC Fuse, were the proper fuse link is selected simultaneously with the line voltage as shown in FIG. 3.
This provides complete flexibility and eliminates the need for special kits and instructions.